A typical communication link has a specified maximum and minimum operating distance between transmitter and receiver. For mobile devices, such as portable communication devices or listening devices, e.g. hearing instruments, that are adapted to communicate with each other via a wireless link, it may happen that a transmitting device and a receiving device are located (intentionally or un-intentionally) out of the specified operating range.
A communication system comprising first and second communication devices comprising a dynamic regulation scheme for adapting transmit power to the signal quality of the link established between the devices is e.g. disclosed in EP 2 211 579 A1. In an embodiment, the system is adapted to use the dynamic power regulation to implement a partial power down of the system, when the two communications devices are located outside the specified operating range (i.e. either too close to each other or too far from each other). When the two devices are too close to each other, the receiver ‘saturates’ because it is not able to handle the received input level.
US 2009/0130991 A1 describes a method of matching the input of an LNA to an antenna over a range of frequencies by maximizing field strength using an adjustable antenna matching network. US 2004/0080372 A1 describes a high frequency amplifier for a mobile phone comprising variable capacitors and resistors at its input and output matching circuits, wherein the gain and frequency response can be automatically tuned to the avoid impact of impedance variation of the lead frame of the mobile phone or resulting from the manufacturing process.